R Type Thermocouple:

Element Combination:

Positive Leg:  Platinum – 13% Rhodium

Negative Leg: Platinum

Temperature:

538 to 1482 ºC

1000 to 2700 ºF

Application:

• The Type R is used in very high temperature applications. 
• It has a higher percentage of Rhodium than the Type S, which makes it more expensive.
• The Type R is very similar to the Type S in terms of performance.
• When used above 1100ºC they must be protected with non-metallic protection tube and ceramic insulators.
• Type R is not suitable for direct insertion into metallic protecting tubes.
• Type R Thermocouples are quite stable and capable of long operating life when used in clean, favorable conditions. 

Continued high temperature usage causes grain growth which can lead to mechanical failure. Negative calibration drift caused by Rhodium diffusion to pure leg as well as from Rhodium volatilization. Type R is used in industry; Type S in the laboratory.